1. Field of the Invention
The invention relates to the field of electronics. More specifically, the invention lies in the area of analog/digital real time seeker processing circuits utilizing imaging capabilities of a charge coupled device (CCD) array in combination with the computing power of a microcomputer (xcexcC).
2. Description of the Prior Art
Before the development of CCDs, microprocessors, and microcomputers, imaging systems for short-range air-to-air missile applications were impractical. Prior to the development of CCD arrays, real-time imaging systems for larger weapons were implemented with television vidicons. Vidicons were constructed of glass tubes, which were excessively bulky for use on gimballed seeker platforms small enough for short-range air-to-air missiles. The advent of the xcexcC also greatly reduced the volume required for the acquisition/tracking electronics. The combination of these two technological advances permitted the packing of both the imaging system and associated acquisition/tracking electronics within a sufficiently small airframe volume.
A missile incorporating these two technologies requires circuitry designed to interface the CCD imaging-system to the imbedded xcexcC-based controller. Specialized video processing techniques are therefore needed to satisfy the required target acquisition ranges for certain types of missiles. Circuitry in the analog video processor disclosed herein optimizes CCD video by use of automatic light control (ALC) and automatic gain control (AGC) systems. Other specialized circuitry of the invention minimizes the synchronous noise inherent in CCD video and extracts targets with sharp edges, which generally indicate man-made objects.
There exists therefore a continuing need for the analog video processor described herein that can efficiently couple a CCD array to a xcexcC acquisition and tracking system.
The invention is a CCD seeker analog video processor having a video preprocessor (VPP) and video processor (VP) circuits cou-pling a xcexcC to a CCD camera and video monitor. The invention is capable of real time tracking and display of a target in white and black images. With the exception of the video monitor, all of these modules were designed for packaging in the small airframe -of a short-range air-to-air missile. The VPP consists of an ALC circuit that controls light to the CCD array, an AGC circuit that controls video signal amplitude, and a display (DP) circuit that provides a video signal to a video monitor. The VPP presents useful video from the CCD camera to the VP for further processing by controlling video signal amplitude and the CCD array exposure to light, and further provides a video image of the scene the CCD seeker is viewing and tracking. The VP consists of. a gradient processor (GP) circuit that detects potential targets with best edges, i.e. edges containing the highest spatial frequency components within the field of view. Because man-made objects (targets) have sharper edges, a contrast: processor (CP) circuit that detects targets as a function of signal amplitude by sampling and subtracting background on either side of a potential target, and an output control (OC) circuit that converts four asynchronous pulse signals from the CP and GP circuits to signal formats that are detectable by synchronous means at the input of xcexcC for input to the xcexcC. The VP converts analog signals to a digital format that is acceptable for the microcomputer to discern-and track a target.
It is therefore a primary object of the invention to couple a CCD seeker array to xcexcC for acquisition and tracking of a target.
Another object of the invention is to incorporate a feedback CCD camera iris control to regulate the amount of light impinging on a CCD array.
Yet another object of the invention is to regulate the amplitude of the CCD camera video signal to be processed.
A further object-is to provide for a video monitor displaying the field of view of the CCD camera.
Yet another object is extract from the CCD video signal a best edge function, those edges containing the highest spatial frequency components within the field of view to detect potential targets via gradient signatures, i.e. higher frequencies indicate sharper edges which probably indicate man-made objects.
Yet a further object of the invention is to detect a target as a function of video signal amplitude via a contrast signature.
Yet a another object of the invention is to convert gradient and contrast asynchronous digital target signals to synchronous digital target signal edges for input to a microcomputer.
These and further objects and more advantageous features will become more readily apparent in view of the attached drawing, the accompanying specification and the appended claims.